President Dmitry Medvedev said on Friday time was running out for the West to come up with new proposals to secure Russia's agreement to a missile defense shield in Europe.

Ahead of talks with U.S. President Barack Obama next week, Medvedev gave a downbeat assessment of global security and international relations at the end of his four-year presidency, saying the "Euro-Atlantic" security community he had hoped to create remained a "myth".

Medvedev, who will be succeeded by Vladimir Putin in May, said Moscow was unconvinced by NATO's argument that the planned missile defense shield was intended as protection against a missile attack by countries such as Iran.

"We have time (for an agreement) but it is running out, and I think that it would be in our mutual benefit to reach mutually acceptable agreements," Medvedev told a security conference.

"The main thing is that we must hear one simple thing - hear it and receive confirmation: 'Respected friends from Russia, our missile defense is not aimed against Russian nuclear forces.' This must be affirmed, not in a friendly chat over a cup of tea or a glass of wine, but in a document."

NATO has offered Russia a role in the project to create an anti-ballistic shield which includes participation by Romania, Poland, Turkey and Spain.

But Moscow says it fears the system could weaken Russia by gaining the capability to shoot down the nuclear missiles it relies on as a deterrent. It wants a legally binding pledge from the United States that Russia's nuclear forces would not be targeted by the system.

Medvedev has said that if the deadlock continues, Moscow will boost its early-warning radar to protect nuclear missile sites, deploy weapons to overcome the shield and potentially target missile defense installations to its south and west.

Some experts and U.S. officials say Russia is overplaying any potential threat.

Former U.S. Defense Secretary William Perry said he believes "the Russians, with high confidence and low cost, could penetrate any ballistic missile defense" the United States might build.

"It is a major, major tragedy that Russian concerns about U.S. ballistic missile defense have had such a corrosive effect on U.S.-Russian relations," he told the conference.

VANCOUVER TO VLADIVOSTOK

Without explicitly naming the United States, Medvedev said the authority of the United Nations had been undermined by powers that tried to bypass the Security Council.

"As long as we are unable to agree in the United Nations, this means that it is faulty or the policies of some states are faulty," he said, condemning calls for military intervention in Syria and Iran and the citing of human rights concerns to try to justify such action.

Medvedev has long been seen as the junior partner in a ruling 'tandem' with Putin, whose tough rhetoric against the West has left its mark on relations. Critics say Medvedev has been unable to push through reforms or leave his mark on policy.

He first proposed the idea of a Euro-Atlantic security treaty linking North America, Europe, Russia and other ex-Soviet republics shortly after taking office in 2008, calling for a new security architecture "from Vancouver to Vladivostok".

Responses have been largely dismissive, with Western governments worrying it would undermine NATO and other groups.

The idea of a "Euro-Atlantic security community" remained a myth for now, "but this myth must become reality. All of us could join this work," said Medvedev, who will meet Obama for talks during a nuclear security summit in South Korea next week.